A. Field of the Invention
This invention relates to a brake rigging system, and more particularly to a brake rigging system which achieves an adequate brake force distribution among all its elements including the brake heads.
B. Description of the Related Art
Most railroad freight cars, use what is known as foundation brake rigging. On the car body, there is an air brake system which provides air to the brake cylinder, which, in turn, supplies a mechanical force, through a system of rods and driving levers to a connection on the standard freight car trucks located at each end of the car. At this point, the force is applied to a truck driving lever system, usually consisting of two driving levers and a connecting rod. The driving levers move brake beams which apply force to the treads of the wheels through renewable friction blocks or brake shoes, retarding the rotation of the wheels.
The conventional brake rigging includes two brake beams, at least one brake cylinder assembly supported by one or both of the brake beams, and a driving lever or linkage assembly so connected between the brake beams and cylinder assembly that actuation of the cylinder assembly moves the brake beams away from one another and into braking engagement with treads of wheels of a railway vehicle truck. U.S. Pat. Nos. 2,996,963 and 3,107,754 each describe an example of such a brake rigging. Commonly, however, a conventional brake rigging is relatively heavy and is therefore responsible for a significant fraction of the power required to move its vehicle truck along railway tracks.
The brake rigging may be xe2x80x9ctruck mountedxe2x80x9d i.e. every truck of the railway car has its own braking mechanism with independent driving means.
There are many brake beams configurations used with the above referred general type of brake rigging, but the most common type of brake beam which is the most commonly used, comprises a compression member, a generally xe2x80x9cVxe2x80x9d shaped tension member having its ends coupled to the ends of the compression member, a brake head linked to the each end of the compression member, two end extensions, each linked at each end of the tension and compression member, by which the brake beam is coupled to the bogie of a railway car and a fulcrum welded to the compression member and tension member, so that the fulcrum remains between the tension and compression members.
The main problem of the above described brake rigging systemxe2x80x94including the above referred brake beamxe2x80x94, is the inadequate distribution of the braking force among the two brake shoes due to the configuration of the brake beam, principally due to the inclination of the fulcrum of the brake beam, through which the driving lever passes.
During use, high torsional moments are induced over the brake beam by the brake rigging, and furthermore, the braking force applied to the fulcrum by the driving lever is not equally distributed along the whole beam, causing a great stress in certain parts and elements,of the brake beam when brakes are applied. These harmful forces are especially high at the ends of the brake beam which is the point where the brake beam is coupled to the bogie and where several components thereof are joined, such as the brake head, the tension member and compression member, therefore the ends of the brake beam become critical points where a lot of harmful forces converge.
This inadequate distribution of forces cause an inadequate distribution of the braking force among the brake shoes and thus different deceleration rates among the wheels of the freight car, making it necessary to apply more pressure to the brake shoes in order to compensate for the wheels having a deficient braking, causing overheating and thermal damage to those wheels.
Moreover, the inadequate orientation that the brake beam keeps with respect to an horizontal axis and consequently, the ineficient actuation of the brake beam over the wheels, produces a nonuniform and incomplete wear of the useful material of the brake shoes, which causes a waste of brake shoe material that could be properly used.
The above referred problem forces the maintenance team to frequently change the brake shoe material which is a waste of time and money.
Another important problem related to the inadequate force distribution among the brake shoes, is the misalignment caused to the wheels when the brakes are applied.
Considering the above referred problems, applicants developed a brake rigging system which adequately distributes the braking force among all its components, thus eliminating all the above related problems.
Applicants brake rigging system comprises: a driving beam having a first and a second end; two driving levers having a first and a second end, each driving lever rotary coupled by its first end to an end of the driving beam, and the second end of each driving lever coupled to a brake head; and linking means for linking said driving beam, to driving means which apply a force to said driving beam to push or pull said driving levers together with the brake heads.
The driving levers can be linked to the brake heads by means of two torsional elements, which can be rotary coupled to an end of a support beam and each linked at and end of one of the driving levers of the brake rigging system; two brake head levers tightly coupled to the torsional elements and each joining a brake head; and two pivot extensions to be coupled to the bogie of a railway car, each tightly coupled to each torsional bar in order to pivotally join the brake beam to the bogie of a railway car.
Also the brake heads may be directly coupled at a central portion of each driving lever, thus eliminating the torsional bars.
Applicants brake rigging system produces a pivotal movement of the brake beam, achieving an uniform force distribution among the whole brake beam and between each brake shoe, eliminating the non-uniform braking among the wheels and the resulting wheel damage.
Additionally, the new brake rigging of the present invention, allows a good adaptation of the brake shoes to the wheel contour, achieving a uniform contact between the brake shoe and the wheels, by which all the useful material in the brake shoe is totally used, eliminating points in the brake shoe where the material is so worn that the metal of the brake shoe head comes in direct contact with the wheel.
Due to the adequate use of all the material of the brake shoe, and to the elimination of the wheel damage, the need for frequent change of the brake shoes and wheels avoided, which helps to achieve great money saving in view of the high maintenance costs caused by said frequent changes, and avoids the waste of useful brake shoe material that still could be used if the thickness of the remaining material were uniform.
And last but not least, the brake rigging system extends the brake beam operative life due to the adequate distributions of force to all the elements of the brake beam, which eliminates stress points which could cause the brake beam to break or collapse.
It is therefore a main object of the present invention, to provide a brake rigging system which adequately distributes the braking force among the whole brake beam
It is also a main object of the present invention to provide a brake rigging system, by which uniform wear of the useful material of the brake shoes achieved.
It is another object of the present invention to provide a brake rigging system by which damage to the wheels of the railway car, produced by an inadequate distribution of the braking force applied to the wheels by the brake shoes through the brake beam is reduced.
It is also a main object of the present invention to provide a brake rigging system which extends the brake beam operative life due to the adequate distribution of force to all the elements of the brake beam, which eliminates stress points which could cause the brake beam to break or collapse.
It is also another object of the present invention to provide a brake rigging system which helps to achieve great money saving in view of the high maintenance costs caused by the frequent changes of the brake shoe material.
These and other object and advantages of the brake rigging system of the present invention will become apparent to those persons having an ordinary skill in the art, from the following detailed description of the embodiments of the invention which will be made with reference to the accompanying drawings.